We present the results of the SuperLupus Survey for transiting hot Jupiter planets, which monitored a single Galactic disk field spanning 0.66 deg2 for 108 nights over three years. Ten candidates ...were detected: one is a transiting planet, two remain candidates, and seven have been subsequently identified as false positives. We construct a new image quality metric, Sj , based on the behavior of 26,859 light curves, which allows us to discard poor images in an objective and quantitative manner. Furthermore, in some cases we are able to identify statistical false positives by analyzing temporal correlations between Sj and transit signatures. We use Monte Carlo simulations to measure our detection efficiency by injecting artificial transits onto real light curves and applying identical selection criteria as used in our survey. We find at 90% confidence level that 0.10+0.27 -- 0.08% of dwarf stars host a hot Jupiter with a period of 1-10 days. Our results are consistent with other transit surveys, but appear consistently lower than the hot Jupiter frequencies reported from radial velocity surveys, a difference we attribute, at least in part, to the difference in stellar populations probed. In light of our determination of the frequency of hot Jupiters in Galactic field stars, previous null results for transiting planets in open cluster and globular cluster surveys no longer appear anomalously low.
High-resolution transmission spectroscopy is a method for understanding the chemical and physical properties of upper exoplanetary atmospheres. Due to large absorption cross-sections, resonance lines ...of atomic sodium D-lines (at 5889.95 and 5895.92 Å) produce large transmission signals. Our aim is to unveil the physical properties of WASP-17b through an accurate measurement of the sodium absorption in the transmission spectrum. We analyze 37 high-resolution spectra observed during a single transit of WASP-17b with the MIKE instrument on the 6.5 m Magellan Telescopes. We exclude stellar flaring activity during the observations by analyzing the temporal variations of Hα and Ca II infrared triplet (IRT) lines. We then obtain the excess absorption light curves in wavelength bands of 0.75, 1, 1.5, and 3 Å around the center of each sodium line (i.e., the light curve approach). We model the effects of differential limb-darkening, and the changing planetary radial velocity on the light curves. We also analyze the sodium absorption directly in the transmission spectrum, which is obtained by dividing in-transit by out-of-transit spectra (i.e., the division approach). We then compare our measurements with a radiative transfer atmospheric model. Our analysis results in a tentative detection of exoplanetary sodium: we measure the width and amplitude of the exoplanetary sodium feature to be σNa = (0.128 ± 0.078) Å and ANa = (1.7 ± 0.9)% in the excess light curve approach and σNa = (0.850 ± 0.034) Å and ANa = (1.3 ± 0.6)% in the division approach. By comparing our measurements with a simple atmospheric model, we retrieve an atmospheric temperature of 15501550 −200+700$^{+170}_{-200}$−200+170 K and radius (at 0.1 bar) of 1.81 ± 0.02 RJup for WASP-17b.
WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary eclipse is the deepest of all transiting planets and has been measured in multiple optical and infrared bands. We obtained a ...z-band eclipse observation with a measured depth of 0.080% + or - 0.029%, using the 2 m Faulkes Telescope South, which is consistent with the results of previous observations. We combined our measurement of the z-band eclipse with previous observations to explore atmosphere models of WASP-19b that are consistent with its broadband spectrum. We use the VSTAR radiative transfer code to examine the effect of varying pressure-temperature profiles and C/O abundance ratios on the emission spectrum of the planet. We find that models with super-solar carbon enrichment best match the observations, which is consistent with previous model retrieval studies. We also include upper atmosphere haze as another dimension in the interpretation of exoplanet emission spectra and find that particles <0.5 mu m in size are unlikely to be present in WASP-19b.
We present ultraviolet, optical and near-infrared observations of the interacting transient SN 2009ip, covering the period from the start of the outburst in 2012 October until the end of the 2012 ...observing season. The transient reached a peak magnitude of M
V
= −17.7 mag, with a total integrated luminosity of 1.9 × 1049 erg over the period of 2012 August-December. The light curve fades rapidly, dropping by 4.5 mag from the V-band peak in 100 d. The optical and near-infrared spectra are dominated by narrow emission lines with broad electron scattering wings, signalling a dense circumstellar environment, together with multiple components of broad emission and absorption in H and He at velocities in the range 0.5-1.2 × 104 km s−1. We see no evidence for nucleosynthesized material in SN 2009ip, even in late-time pseudo-nebular spectra. We set a limit of <0.02 M on the mass of any possible synthesized 56Ni from the late-time light curve. A simple model for the narrow Balmer lines is presented and used to derive number densities for the circumstellar medium in the range ∼109-1010 cm−3. Our near-infrared data do not show any excess at longer wavelengths, and we see no other signs of dust formation. Our last data, taken in 2012 December, show that SN 2009ip has spectroscopically evolved to something quite similar to its appearance in late 2009, albeit with higher velocities. It is possible that neither of the eruptive and high-luminosity events of SN 2009ip were induced by a core collapse. We show that the peak and total integrated luminosity can be due to the efficient conversion of kinetic energy from colliding ejecta, and that around 0.05-0.1 M of material moving at 0.5-1 × 104 km s−1 could comfortably produce the observed luminosity. We discuss the possibility that these shells were ejected by the pulsational pair instability mechanism, in which case the progenitor star may still exist, and will be observed after the current outburst fades. The long-term monitoring of SN 2009ip, due to its proximity, has given the most extensive data set yet gathered of a high-luminosity interacting transient and its progenitor. It is possible that some purported Type IIn supernovae are in fact analogues of the 2012b event and that pre-explosion outbursts have gone undetected.
We present high-precision radial velocity observations of WASP-17 throughout the transit of its close-in giant planet, using the MIKE spectrograph on the 6.5 m Magellan Telescope at Las Campanas ...Observatory. By modeling the Rossiter-McLaughlin effect, we find the sky-projected spin-orbit angle to be Delta *l = 167.4 ? 11.2 deg. This independently confirms the previous finding that WASP-17b is on a retrograde orbit, suggesting it underwent migration via a mechanism other than just the gravitational interaction between the planet and the disk. Interestingly, our result for Delta *l differs by 45 ? 13 deg from the previously announced value, and we also find that the spectroscopic transit occurs 15 ? 5 minutes earlier than expected, based on the published ephemeris. The discrepancy in the ephemeris highlights the need for contemporaneous spectroscopic and photometric transit observations whenever possible.
ABSTRACT
We report the discovery of NGTS-21b , a massive hot Jupiter orbiting a low-mass star as part of the Next Generation Transit Survey (NGTS). The planet has a mass and radius of 2.36 ± 0.21 MJ ...and 1.33 ± 0.03 RJ, and an orbital period of 1.543 d. The host is a K3V (Teff = 4660 ± 41 K) metal-poor (Fe/H = −0.26 ± 0.07 dex) dwarf star with a mass and radius of 0.72 ± 0.04 M⊙ and 0.86 ± 0.04R⊙. Its age and rotation period of $10.02^{+3.29}_{-7.30}$ Gyr and 17.88 ± 0.08 d, respectively, are in accordance with the observed moderately low-stellar activity level. When comparing NGTS-21b with currently known transiting hot Jupiters with similar equilibrium temperatures, it is found to have one of the largest measured radii despite its large mass. Inflation-free planetary structure models suggest the planet’s atmosphere is inflated by $\sim \! 21{{\ \rm per\ cent}}$, while inflationary models predict a radius consistent with observations, thus pointing to stellar irradiation as the probable origin of NGTS-21b’s radius inflation. Additionally, NGTS-21b’s bulk density (1.25 ± 0.15 g cm–3) is also amongst the largest within the population of metal-poor giant hosts (Fe/H < 0.0), helping to reveal a falling upper boundary in metallicity–planet density parameter space that is in concordance with core accretion formation models. The discovery of rare planetary systems such as NGTS-21 greatly contributes towards better constraints being placed on the formation and evolution mechanisms of massive planets orbiting low-mass stars.
ABSTRACT
We present multi‐epoch medium‐resolution observations of two M4.5 candidate members in the halo of the ∼8 Myr η Chamaeleontis open cluster. During six months of observations, both stars ...exhibited variations in their Hα line profiles on time‐scales of days to months, with at least one episode of substantial activity attributable to accretion from a circumstellar disc. We derive an accretion rate of ∼10−8.7 M⊙ yr−1 for this event, with a rate of ∼10−10.6 M⊙ yr−1 in quiescence. Episodic accretion like that observed here suggests existing surveys of accreting weak‐lined T Tauri stars in young clusters are likely incomplete and that gas dissipation time‐scales calculated from the fraction of accreting objects are underestimates.
We present a strong case for a transiting hot Jupiter planet identified during a single-field transit survey toward the Lupus Galactic plane. The object, Lupus-TR-3b, transits a V = 17.4 K1 V host ...star every 3.91405 days. Spectroscopy and stellar colors indicate a host star with effective temperature 5000 plus or minus 150 K, with a stellar mass and radius of 0.87 plus or minus 0.04 M unk and 0.82 plus or minus 0.05 R unk, respectively. Limb-darkened transit fitting yields a companion radius of 0.89 plus or minus 0.07 R unk and an orbital inclination of 88.3 super(+) sub(-) super(1) sub(0) super(.) sub(.) super(2) sub(8) deg. Magellan 6.5 m MIKE radial velocity measurements reveal a 2.4 sigma K = 114 plus or minus 25 m s super(-1) sinusoidal variation in phase with the transit ephemeris. The resulting mass is 0.81 plus or minus 0.18 M unk and density 1.4 plus or minus 0.4 g cm super(-3). gamma -band PANIC image deconvolution reveals a V greater than or equal to 21 red neighbor 0.4 unk away which, although highly unlikely, we cannot conclusively rule out as a blended binary with current data. However, blend simulations show that only the most unusual binary system can reproduce our observations. This object is very likely a planet, detected from a highly efficient observational strategy. Lupus-TR-3b constitutes the faintest ground-based detection to date, and one of the lowest mass hot Jupiters known.
Phase Light Curves for Extrasolar Jupiters and Saturns Dyudina, Ulyana A; Sackett, Penny D; Bayliss, Daniel D. R ...
Astrophysical journal/The Astrophysical journal,
01/2005, Letnik:
618, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We predict how a remote observer would see the brightness variations of giant planets similar to those in our solar system as they orbit their central stars. Our models are the first to use measured ...anisotropic scattering properties of solar system giants and the first to consider the effects of eccentric orbits. We model the geometry of Jupiter, Saturn, and Saturn's rings for varying orbital and viewing parameters, using scattering properties for the (forward scattering) planets and (backward scattering) rings as measured by the Pioneer and Voyager spacecraft at 0.6-0.7 mu m. Images of the planet with and without rings are simulated and used to calculate the disk-averaged luminosity varying along the orbit; that is, a light curve is generated. We find that the different scattering properties of Jupiter and Saturn (without rings) make a substantial difference in the shape of their light curves. Saturn-sized rings increase the apparent luminosity of a planet by a factor of 2-3 for a wide range of geometries, an effect that could be confused with a larger planet size. Rings produce asymmetric light curves that are distinct from the light curve that the planet would have without rings, which could resolve this confusion. If radial velocity data are available for the planet, the effect of the ring on the light curve can be distinguished from effects due to orbital eccentricity. Nonringed planets on eccentric orbits produce light curves with maxima shifted relative to the position of the maximum phase of the planet. Given radial velocity data, the amount of the shift restricts the planet's unknown orbital inclination and therefore its mass. A combination of radial velocity data and a light curve for a nonringed planet on an eccentric orbit can also be used to constrain the surface scattering properties of the planet and thus describe the clouds covering the planet. We summarize our results for the detectability of exoplanets in reflected light in a chart of light-curve amplitudes of nonringed planets for different eccentricities, inclinations, and azimuthal viewing angles of the observer.
We present the results of a deep, wide-field transit survey targeting 'Hot Jupiter' planets in the Lupus region of the Galactic plane conducted over 53 nights concentrated in two epochs separated by ...a year. Using the Australian National University 40-inch telescope at Siding Spring Observatory (SSO), the survey covered a 0.66 deg2 region close to the Galactic plane (b = 11°) and monitored a total of 110,372 stars (15.0 <= V <= 22.0). Using difference imaging photometry, 16,134 light curves with a photometric precision of s < 0.025 mag were obtained. These light curves were searched for transits, and four candidates were detected that displayed low-amplitude variability consistent with a transiting giant planet. Further investigations, including spectral typing and radial velocity measurements for some candidates, revealed that of the four, one is a true planetary companion (Lupus-TR-3), two are blended systems (Lupus-TR-1 and 4), and one is a binary (Lupus-TR-2). The results of this successful survey are instructive for optimizing the observational strategy and follow-up procedure for deep searches for transiting planets, including an upcoming survey using the SkyMapper telescope at SSO.
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